CarbTune Question | GTAMotorcycle.com

CarbTune Question

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NuggyBuggy

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I bought a Carbtune II from another user here about two weeks ago. I haven’t been able to test it out as both my bike and MityVac are at the cottage, but I did try sucking on the hoses. Somewhat to my surprise the rods did not move at all, but I am really not sure how much vacuum is produced by a running engine. The PO had installed the little barbs (restrictors?) that join to another smaller length of hose as per the instructions, but removing those from the hose didn’t change anything. The situation is the same on all the hoses.

Should I have been able to move those rods in this manner or does it require more vacuum then an average person could produce ?
 
Never tried giving my carbtune a hummer but I doubt a person could produce enough pressure through the small diameter of the hoses to move the bars.
 
The “restrictors” are there so that the gauges give a smooth accurate reading.Without them the stainless rods would fluctuate up and down wildly with each vacuum pulse from the cylinder. Not sure if you would be a able to such
k hard enough to move those stainless rods, l’ve never tried but I think not.
 
If using a mercury gauge, full scale is close to 2'. You can move the column pretty easily (although sucking on mercury vapor is obviously a dumb idea). Since full scale on the carbtune is much less distance, you need to get a decent vacuum before anything starts to move. That being said, here is someone sucking on a carbtune and it moves.


With the restrictors a quick puff may not make it through but leave the vacuum on for a few seconds and the restrictor should be a non-issue (assuming it is not completely plugged).
 
GreyGhost said:
If using a mercury gauge, full scale is close to 2'. You can move the column pretty easily (although sucking on mercury vapor is obviously a dumb idea). Since full scale on the carbtune is much less distance, you need to get a decent vacuum before anything starts to move. That being said, here is someone sucking on a carbtune and it moves.


With the restrictors a quick puff may not make it through but leave the vacuum on for a few seconds and the restrictor should be a non-issue (assuming it is not completely plugged).
Click to expand...
Interesting. The guy did say he had the restrictors in too, and I didn’t get the impression it was very hard to draw that rod up.
 
Wow, thanks @Bobo . I am embarrassed to say I did not,but just tried it. Initially they did not drop at all. Then I turned it up and down again, and they did drop to roughly the 16 mark, whatever that means, Not smoothly, a little jerkily. I kept turning it up and down and they seemed to drop down a little more smoothly, but still seem a little sticky. Now I am shaking it up and down getting the rods to move up and down in their tubes, this seems to be helping them move more freely.

They still seem to be sticking, when upside down you can sometimes see a rod drop a bit, then after a second drop a bit more.

I can now draw the rods up a bit by applying sucking pressure when the tool is upright, but it sure isn’t easy, but at least they are moving now. Before they wouldn’t move a bit.

I think I saw somewhere that there’s something you can do by removing the top, I may look into this.
 
i would just shake it to loosen the rods up a bit. It’s been sitting for a few years.If you remove the rods to clean them , make sure you put them back into the tubes you removed them from , I think they’re calibrated.
 
Just realized if you turn it upside down or shake it with the restrictors on , the rods probably won’t move much because it has to force the air through those tiny restrictors which are literally the size of a hair. Try taking the restrictors and or hoses off when you turn it upside down
 
FWIW I had my CarbTune for years before I had a reason to actually use it, and when I finally did it still worked great.

The manual does have a section at the end regarding disassembly, but if it were me I'd wait until I confirm that it's necessary
 
After @Bobo ’s suggestion helped free the rods a bit, I found an article about cleaning the rods and guides. The argument is that “engine blow-back forces small amounts of fuel & oil vapour into the vacuum gauge tubes which, when dry, leaves behind a residue that may cause rods to stick or move less freely in their guides”, which makes sense. There is the faintest odour of fuel coming from the tubes.

I haven’t decided if I will wait unti I can hook it up to my bike (hopefully this weekend) or just clean them now.

Here’s the article on cleaning. It is a lot more detailed than the manual.
 
That Carbtune has only been used once so I don’t think it will be very dirty inside. I would try using it and see what happens. See if the rods rise in the columns when it’s running, they should flutter up and down a bit , maybe 1 or 2mm but that’s normal and you know that it’s working properly
 
Bobo said:
That Carbtune has only been used once so I don’t think it will be very dirty inside. I would try using it and see what happens. See if the rods rise in the columns when it’s running, they should flutter up and down a bit , maybe 1 or 2mm but that’s normal and you know that it’s working properly
Click to expand...
Hey - Do you know the gentleman who sold me the unit?
 
So I bought some aquarium air line tubing and a 4-way gang valve and hooked up my MityVac to the Carbtune. It looks like the Carbtune leaks air because the readings on all the channels drop fairly quickly as soon as I stop applying vacuum. At higher levels of vacuum you can hear a brr-brr-brr sound that seems to come from somewhere near the top of the Carbtune, as if air is forcing is way out.

Should the Carbtune hold its readings and associated vacuum, or is it really just a readout of vacuum at one point in time, requiring a constant source of vacuum ?
I know my MityVac will hold vacuum and I know it’s not my hoses or the gang fitting. Maybe the hoses are a little too stretched out at the Carbtune fittings to provide a proper seal ?

I did take the rods out and cleaned them with a cloth; before I did this the rods would drop down in quite a jerky fashion and one of them tended to read much lower than the others, after cleaning the rods drop quite a bit more smoothly (but still a bit jerky), and the rod which tended to read low now seems more in line.


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